High-speed sheet feeders are well known in the art. See, for example, Wright et al. (U.S. Pat. No. 6,095,513) which discloses a bottom sheet feeder for feeding sheets from the bottom of a vertical sheet stack wherein each sheet of paper is substantially horizontal in the stack. To operate any high-speed sheet feeder effectively, sheet stacks must be delivered and supplied to the sheet feeder in an efficient manner.
To operate efficiently, a high-speed sheet feeder requires a large stack of paper to operate at optimum speed, but a problem with a large vertical stack is that it necessitates a sheet feeder that is unacceptably high above floor-level if sheets are fed from the top of the paper stack. In the case of a bottom sheet feeder, an unacceptable weight would be placed on each sheet fed from the bottom of a large vertical paper stack. When the weight of the vertical stack of paper is too great, the bottom sheet becomes frictionally engaged with an overlying sheet and therefore two or more sheets are frequently fed from the stack (in the industry this problem is called “doubling”). Doubling causes jams and necessitates shutdowns to clear the jams, and doubling furthermore reduces the smooth flow of paper and limits the rate at which sheets are fed into the high-speed sheet feeder. In addition to the problem of doubling, the bottom sheet feeder may not feed at all, which is known as the “stalling” problem. Pressurized air can somewhat relieve these bottom feeder problems, as seen in Strobel Jr. (U.S. Pat. No. 3,934,869), but still the vertical stack of paper cannot be large.
It is known in the art to use a document loading cart that carries a horizontal stack of paper to a sheet feeder, instead of a vertical stack. For example, the GBR 470 marketed by GBR Systems Corporation is a document loading module of that type. Unfortunately, document loading carts of that type have a number of drawbacks. For example, those carts must remain in place while the stack of paper is being fed to the sheet feeder, which prevents the cart from being used to quickly obtain another stack of paper. Conceivably, a second cart of the same type could be used to obtain another stack of paper, but such a solution would entail much unnecessary duplication of equipment (e.g., both carts would require a frame, wheels, stack advancing means, et cetera). Furthermore, existing carts of that type (e.g., like the GBR 470) are inefficient in that many parts, such as stack advancement means, could instead be permanently located at the sheet feeder instead of being unnecessarily carted around. A further problem with those old sheet feeding carts is that they are designed to interface only with bottom sheet feeders instead of sheet feeders specifically designed to accommodate a horizontal stack of paper, and this lack of compatibility entails unnecessary sheet feeding steps.